<template>
  <div class="slider" ref="slider">
    <div class="slider-group" ref="sliderGroup">
      <slot></slot>
    </div>
    <div class="dots">
      <span class="dota" v-for="(item, index) in dots" :class="{active: currentPageIndex === index}"></span>
    </div>
  </div>
</template>

<script type="text/ecmascript-6">
  import BScroll from 'better-scroll'
  import {addClass} from 'common/js/dom.js'
  export default {
    data() {
      return {
        dots: [],
        currentPageIndex: 0
      }
    },
    props: {
      loop: {
        type: Boolean,
        default: true
      },
      autoPlay: {
        type: Boolean,
        default: true
      },
      interval: {
        type: Number,
        default: 4000
      }
    },
    mounted() {
      setTimeout(() => {
        this._setSliderWidth()
        this._initDots()
        this._initSlider()
        if (this.autoPlay) {
          this._play()
        }
      }, 20)
      window.addEventListener('resize', () => {
        if (!this.slider) {
            return
        }
        this._setSliderWidth(true)
        this.slider.refresh()
          })
    },
    destroyed() {
      clearTimeout(this.timer)
    },
    methods: {
      _setSliderWidth(isResize) {
        this.children = this.$refs.sliderGroup.children
        let width = 0
        let sliderWidth = this.$refs.slider.clientWidth
        for (let i = 0; i < this.children.length; i++) {
          let child = this.children[i]
          addClass(child, 'slider-item')
          child.style.width = sliderWidth + 'px'
          width += sliderWidth
        }
        if (this.loop && !isResize) {
          width += 2 * sliderWidth
        }
        this.$refs.sliderGroup.style.width = width + 'px'
      },
      _initDots() {
        this.dots = new Array(this.children.length)
      },
      _initSlider() {
        this.slider = new BScroll(this.$refs.slider, {
          scrollX: true,
          scrollY: false,
          momentum: false,
          snap: true,
          snapLoop: this.loop,
          snapThreshold: 0.3,
          snapSpeed: 400
        })
        this.slider.on('scrollEnd', () => {
          let pageIndex = this.slider.getCurrentPage().pageX
          if (this.loop) {
            pageIndex -= 1
          }
          this.currentPageIndex = pageIndex
          if (this.autoPlay) {
            clearTimeout(this.timer)
            this._play()
          }
        })
      },
      _play() {
        let pageIndex = this.currentPageIndex + 1
        if (this.loop) {
          pageIndex += 1
        }
        this.timer = setTimeout(() => {
          this.slider.goToPage(pageIndex, 0, 400)
        }, this.interval)
      }

    }
  }
</script>

<style scoped lang="stylus" rel="stylesheet/stylus">
  .slider
    width: 100%
    position: relative
    overflow: hidden
    white-space: nowrap
    margin-top 10px
    .slider-group
      .slider-item
        box-sizing: border-box
        float: left
        text-align center
        overflow hidden
        a
          display block
          width 100%
          overflow hidden
          text-decoration none
          img
            display: inline-block
            width: 100%

  .dots
    position: absolute
    right: 0
    left: 0
    bottom: 12px
    text-align: center
    .dota
      display: inline-block
      width: 6px
      height: 6px
      border-radius: 3px
      background-color: rgba(255, 255, 255 0.7);
      margin: 5px
      &.active
        width: 20px


</style>
